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Homework Help: Dyn Transformer voltage drop

  1. Jan 29, 2015 #1
    1. The problem statement, all variables and given/known data

    A 3MVA 11kV/415V 3 Phase Transformer has the following parameters
    +ve sequence resistance = 0.00355pu
    +ve sequence reactance = 0.0901pu

    Primary PHASE current to the transformer is 55A and the load power factor on secondary is 0.85 lagging. Calculate voltage Drop

    The attempt at a solution

    R = 0.00355pu = 0.355%
    X = 0.0901pu = 9.01%

    Secondary current (star so line and phase current will be same) = 55 * 11000/415 = 1457.83A

    R(ohms) = (10*%R*kVsecondary2)/Txfr kVA = (10*0.3555*0.4152)/3000 = 0.0002038Ω

    X(ohms) = (10*%X*kVsecondary2)/kVA = (10*9.01*0.4152)/3000 = 0.0051725Ω

    Φ = cos^-1(0.85) = 31.788°

    Volt Drop = Sqrt(3) * 1457.83 * (0.0002038*0.85 + 0.0051725*sin(31.788)) = 7.32V

    Does this mean that the voltage to the load will be 415-7.32 = 407.68V?? This is the bit I would like confirming if the remainder of the calculations happen to be correct?

    Thank you :)
  2. jcsd
  3. Feb 3, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
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